Such MEMS components are used, for example, as loudspeakers as part of a wide variety of applications. Due to their miniaturized design and the possibility of integration of additional functionalities at very low manufacturing costs, MEMS loudspeaker components are becoming increasingly important economically.
Most of the MEMS components on the market for detection and/or generation of pressure pulses are equipped with a preferably large-scale diaphragm in parallel to the plane of the chip or substrate. In the configuration as a microphone, this diaphragm is excited to vertical (out-of-plane) vibrations by the sound pressure. Deflections of the diaphragm are then detected capacitively, for example, as a microphone signal. This principle is applied conversely in the case of the configuration as a loudspeaker. In this case, the diaphragm is excited capacitively, for example, to vertical (out-of-plane) vibrations, resulting in pressure pulses, i.e., sound waves.
These diaphragm-based MEMS components have proven to be problematical in many regards.
Suspension of the diaphragm necessitates bending or warping of the diaphragm, which results in nonlinearities of the microphone signal or the loudspeaker signal and thus has negative effects on the performance of the component. The thinner the diaphragm, the better is the performance of the component. Accordingly, the diaphragm is very fragile and sensitive to mechanical stresses such as impact and knocking effects. The performance of the component is thus in contrast with its robustness.
The detection direction or the drive direction and the displacement movement are similarly oriented in the case of diaphragm-based components. The given facts of the volume displacement are thus linked to the given facts of the detection or drive. In the case of a capacitive loudspeaker component, this results in the loudspeaker performance essentially depending on the energy consumption of the component. In other words, the loudspeaker performance is better, the larger the displacement volume, which is determined here by the gap distance between the diaphragm and the counter electrode. However, the greater the gap distance, the higher is also the energy consumption since high electrostatic forces are needed to trigger the diaphragm accordingly.
German Published Patent Appln. No. 10 2010 029 936 provides a capacitive MEMS microphone component whose layered structure includes at least three function layers. A sound opening, which opens into a cavity beneath the first function layer, is provided in the first function layer. This cavity extends essentially over the second function layer, in which a diaphragm and a counter element are formed, namely in such a way that the diaphragm delimits the cavity on at least one side and is deflectable in the plane of the layer. The diaphragm functions as the first electrode of a microphone capacitor, and the counter element functions as the carrier of a counter electrode of the microphone capacitor. At least one vent opening for the microphone structure is formed beneath the cavity in the third function layer.
In the case of the MEMS microphone component described here, the sound pressure acting on the component perpendicularly to the planes of the layers produces a diaphragm movement oriented in parallel to the planes of the layers of the component.